The present invention relates to microelectronic packaging and more particularly relates to methods of making connectors and packaged microelectronic components. In various microelectronic devices, it is desirable to provide a connection between two components, which can accommodate relative movement between the components. For example, where a semiconductor chip is mounted to a circuit board, thermal expansion and contraction of the chip and circuit board can cause the contacts on the chip to move relative to the corresponding electrically conductive features of the circuit board. This can occur during service and can also occur during manufacturing operations as, for example, during soldering operations on the circuit board.
As illustrated in certain preferred embodiments of U.S. Pat. No. 5,518,964 (xe2x80x9cthe ""964 patentxe2x80x9d) movable interconnections between elements such as a semiconductor chip and another element can be provided by first connecting leads between the elements and then moving the elements away from one another so as to bend the leads. For example, a connection component may incorporate a dielectric body and leads extending along a bottom surface of the dielectric body. The leads may have first or fixed ends permanently attached to the dielectric element and connected to electrically conductive features such as terminals, traces or the like on the dielectric body. The leads may also have second ends releasably attached to the dielectric body. The dielectric body, with the leads thereon, may be juxtaposed with the chip and the second ends of the leads may be bonded to contacts on the chip. Following bonding, the dielectric body and chip are moved away from one another, thereby bending the leads. During or after movement, a curable material such as a liquid composition is introduced between the elements. This is cured to form a compliant dielectric layer such as an elastomer or gel surrounding the leads. The resulting packaged semiconductor chip has terminals on the dielectric body connection component which are electrically connected to the contacts on the chip but which can move relative to the chip so as to compensate for thermal effects. For example, the packaged chip may be mounted to a circuit board by solder-bonding the terminals to conductive features on the circuit board. Relative movement between the circuit board and the chip due to thermal effects is taken up in the moveable interconnection provided by the leads and the compliant layer.
Numerous variations of these processes and structures are disclosed in the ""964 patent. For example, the package-forming process can be conducted on a wafer scale, so that the numerous semiconductor chips in a unitary wafer are connected to connection components in one sequence of operations. The resulting packaged wafer is then severed so as to provide individual units, each including one or more of the chips and portions of the dielectric body associated therewith. Also, the leads may be formed on the chip or wafer rather than on the dielectric body. In further embodiments, also disclosed in the ""964 patent, a connector for use in making connections between two other microelectronic elements is fabricated by a generally similar process. For example, in one embodiment a dielectric body having terminals and leads as discussed above is connected to terminal structures on a temporary sheet. The temporary sheet and dielectric body are moved away from one another so as to bend the leads, and a liquid material is introduced around the leads and cured so as to form a compliant layer between the temporary sheet and the dielectric body. The temporary sheet is then removed, leaving the tip ends of the terminal structures projecting from a surface of the compliant layer. Such a component may be used, for example, by engaging it between two other components. For example, the terminal structures may be engaged with a semiconductor chip, whereas the terminals on the dielectric body may be engaged with a circuit panel or other microelectronic component. Thus, the broad invention taught in the ""964 patent offers numerous desirable ways of making electrical interconnections and connectors.
Additional variations and improvements of the processes taught in the ""964 patent are disclosed in commonly assigned U.S. Pat. Nos. 5,578,286; 5,830,782; and 5,688,716 and in copending, commonly assigned U.S. patent application Ser. No. 08/690,532, filed Jul. 31, 1996 and Ser. No. 09/271,688, filed Mar. 18, 1999, the disclosures of which are hereby incorporated by reference herein.
In one aspect of the present invention, a component for making microelectronic connections comprises a first element having a dielectric material defining a first surface and a plurality of leads having elongated trace portions extending over the first surface and secured to the dielectric element. Each lead has a curved releasable portion extending over the first surface. The releasable portion has a tip end remote from the elongated portion. The releasable portion is releasable from the first surface while the elongated portion remains secured to the semiconductor body. The releasable portion is desirably curved in a plane parallel to the plane of the first surface of the first dielectric element. Thus, leads are provided with an elongated trace portion for routing the lead on the first element, while also providing a releasable portion.
The component desirably includes a plurality of conductive terminal structures adapted for connection to an external substrate and the leads are electrically connected to the terminal structures. Each of the terminal structures may be secured to the first element and disposed at an end of the elongated portion remote from the tip end. The first element desirably comprises a sheet of dielectric material, with the conductive terminal structures extending through the sheet. The sheet of dielectric material is preferably flexible in certain embodiments. In certain embodiments, each lead has an electrically conductive bonding material at the tip end. In certain embodiments, the leads include gold and the bonding material comprises tin, germanium and silicone.
In certain preferred embodiments, the first element comprises a plurality of tiles. The elongated portions of the leads extend outwardly toward the periphery of the first element. The releasable portions of the leads may be disposed in a central area of the first element. The releasable portions of the leads may be disposed in a peripheral area of the first element.
In certain preferred embodiments, the component comprises a support structure having a degradable connecting layer.
In further aspects of the present invention, a semiconductor element comprises a semiconductor body having a surface, contacts and circuits within the body connected to the contacts. The element has a plurality of leads having terminal ends connected to the contacts, elongated trace portions extending over the surface of the semiconductor body and secured to the semiconductor body, and curved releasable portions tip ends remote from the contact ends. The releasable portion of each lead is releasable from the surface of the semiconductor body while the elongated portion remains secured to the semiconductor body. A semiconductor element is provided with elongated trace portions so as to route the lead over the surface of the semiconductor body.
Each lead may have an electrically conductive bonding material at the tip end. The leads may include gold and the bonding material may comprise tin, germanium or silicone. The semiconductor body may comprise a semiconductor chip. The semiconductor body may also comprise a semiconductor wafer.
In certain preferred embodiments, the releasable portion is curved in a plane parallel to the plane of the surface of the semiconductor body.
In certain preferred embodiments, the semiconductor body comprises a semiconductor wafer incorporating a plurality of chips and each chip has a top surface and contacts disposed in a central region of the chip top surface. The elongated portion comprise trace portions extending outwardly from the contacts. In other embodiments, the elongated portions comprise trace portions extending inwardly from contacts adjacent a peripheral region of the chip top surface.
In further aspects of the present invention, a method of making a semiconductor assembly comprises forming leads in place on a semiconductor body having a surface, contacts and circuits within the body connected to the contacts. The contacts include at least one set of contacts exposed at the surface so that the contacts belonging to the set are in proximity to one another. The leads are formed so as to overlie the surface. The step of forming includes depositing a first lead-forming metal over the surface so as to form a first conductor connected to a first contact of the at least one set of contacts. A dielectric material is deposited so as to overlie the first conductor and the first contact. A second lead-forming metal is deposited so as to form a second conductor overlying the first conductor and in contact with a second contact of said at least one set of contacts, whereby the dielectric layer insulates the first conductor from the second conductor. A conductive structure having a first conductor and a second conductor insulated from one another is formed in place on a semiconductor body.
The semiconductor body may have a passivation layer defining the surface. The method may include providing openings in the passivation layer aligned with the first contacts and the second contacts. The step of forming leads may include depositing a sacrificial layer before the step of depositing the first lead-forming metal. The sacrificial layer may comprise a passivation layer on the semiconductor body so that the passivation layer defines the surface on the semiconductor body. A first opening is desirably formed in the sacrificial layer before the step of depositing the first lead-forming metal so that the first opening is aligned with the first contact. The first lead-forming metal may be deposited so as to form an elongated lead and may include depositing metal in the first opening.
The dielectric material may be deposited over the lead-forming metal, including selectively patterning the dielectric material. The selective patterning may include removing portions of the dielectric material aligned with the second contact. The portions of the sacrificial layer aligned with the second contact are desirably removed to form a second opening before the step of depositing the second lead-forming metal. The second lead-forming metal is deposited in the opening. The second lead-forming metal may be deposited so as to form elongated leads.
In certain preferred embodiments, the step of removing portions of the sacrificial layer includes removing portions so as to leave anchors connecting the first conductor to the surface of the semiconductor body. The anchors desirably releasably connect the first conductor to the surface of the semiconductor body.
In certain preferred embodiments, the semiconductor body includes at least one electronic element connected to the set of contacts. The first lead-forming metal, the dielectric material and the second lead-forming metal are desirably deposited so as to form an elongated multi-conductor lead.
In a further aspect of the present invention, a semiconductor element comprises a semiconductor body having a first internal electronic element connected to a set of contacts exposed at a surface of the semiconductor body so that the contacts belonging to said set are in proximity to one another. A conductive structure overlies the surface and is connected to the set of contacts. The conductive structure comprises a first conductor connected to a first contact of the set of contacts and a second conductor is connected to a second contact of the set of contacts.
In certain preferred embodiments, the semiconductor body comprises a semiconductor wafer. The semiconductor wafer desirably incorporates a plurality of semiconductor chips and one of the chips has the set of contacts. At least one other of the chips may have a set of contacts connected to a second internal electronic element.
In certain preferred embodiments, the conductive structure comprises a second conductor overlying a first conductor and the first conductor and second conductor comprise elongated conductive elements. The conductive structure desirably comprises a first dielectric layer disposed between the first conductor and the second conductor and the dielectric layer comprises an elongated element of dielectric material, so that the conductive structure comprises a multi-conductor lead. The conductive structure may include a signal conductor and a ground plane conductor. The conductive structure may include a first signal conductor and a second signal conductor.
In certain preferred embodiments, the conductive structure has a second dielectric layer and a third conductor.
In certain preferred embodiments, the first conductor has a tip end remote from the first contact and an anchor is connected to the tip end and to the semiconductor element so that the anchor releasably connects the tip end to the semiconductor body. The semiconductor element may comprise a sacrificial layer having holes aligned with the first contact and the second contact. The sacrificial layer may comprise a passivation layer. The semiconductor body, in certain embodiments, has a passivation layer.